A variety of packers are used in wellbores to isolate specific wellbore regions. A packer is delivered downhole on a conveyance and expanded against the surrounding wellbore wall to isolate a region of the wellbore. Once set against the surrounding wellbore wall, the packer can be subjected to substantial heat, pressures and forces. Consequently, flexible rubber packer layers can undergo undesirable extrusion which has a detrimental effect on the function of the packer.
Some packers employ anti-extrusion layers to limit the undesirable extrusion. However, expansion/inflation of the packer under high temperature and high-pressure conditions can cause unwanted movement and/or disruption of the anti-extrusion layer. Often, existing packer designs are not suitable for controlling anti-extrusion layer movement during packer inflation and particularly during multiple inflation cycles.
Undesirable movement of the anti-extrusion layer can be induced by a variety of factors related to operation of the packer in a downhole environment. By way of example, rubber materials may creep under the influence of inflation pressure which can result in unwanted additional expansion of the anti-extrusion layer and an undesirable shortening ratio. Expansion of the packer also can cause disorganization of anti-extrusion layer fibers which again increases the shortening ratio. The crossing or disruption of fibers in the anti-extrusion layer also may create high friction points that again influence the shortening ratio. The combination of excessive friction and unwanted local shortening ratio creates a substantial pulling force on the anti-extrusion layer at the packer extremities. If the pulling force is not controlled or countered, the anti-extrusion layer can be pulled free of the packer extremities or otherwise damaged in a manner that detrimentally affects the functionality of the packer.